zlilz Posted October 28, 2006 Share Posted October 28, 2006 I'm almost at the step where I want to take my 91 LS to the dealer and have them diagnose and fix it. Any ideas on where to start looking for problems would help. 2 months ago, I changed the timing belt myself. After the timing belt change, CEL error codes 13, 25 and 26 would show up occasionally. It didn't affect driving at all so I just ignored it. I noticed that sometimes driving on the highway, my foot would be in the same position, but for a second it felt like i lifted my foot off the gas pedal and placed it back on. Fast forward to now. The car still has the cel error codes. There seems to be two problems. Are they related? Problem 1: It starts fine and most of the time it's perfect. When the temperature is normal, sometimes all of the sudden the engine would act up. When the car is idling, all of the sudden as if the engine was no longer getting any air and was suffocating, the rpms will drop to 200 and stay that way for a second. Then the car will act as if the gas pedal was being pressed. It will rev up to about 1300 and then drop down to 600. Problem 2: While driving, all of the suddenly I loose power. Keeping my foot on the gas, there are periods when the engine seems to pick up and move and periods where nothing happens at all. Stepping and letting go of the gas pedal rapidly is very jerky but it seems to make the car move. I've looked around the engine and noticed the following: Spark plug wires are all under 25k resistance. The spark plugs on the passenger side bank all had a slightly damp black (carbon?) stuff on it. They do look a little old. The radiator cap has cracks in the rubber The transmission fluid is about .75 inches higher than the hot limit when the transmission is hot. I changed the rotor and the distributor a while back so they are fine. Resistance of the MAF is normal (according to the repair manual) The throttle position sensor's closed and .4mm open are normal. When it's fully open, it's an infinite resistance Engine coolant sensor is fine Using a timing gun and attaching it to spark plug wire 6, I see a 5 btdc which I know it's suppose to be higher than that ICV has a resistance of 50 So any ideas on what to look at next or replace? ECU? Fuel pump? TPS? ICV? changing the timing? Quote Link to comment Share on other sites More sharing options...
bartkat Posted October 28, 2006 Share Posted October 28, 2006 How's the MAF? Quote Link to comment Share on other sites More sharing options...
LScott400 Posted October 28, 2006 Share Posted October 28, 2006 Have the coils ever been replaced? Quote Link to comment Share on other sites More sharing options...
zlilz Posted October 28, 2006 Author Share Posted October 28, 2006 The MAF resistance was within tolerance of the manual when I took it out to test it. I tested the resistance of both coils and they were within tolerance also. Would it be possible for a part's resistance to be within tolerance but the part is bad? Quote Link to comment Share on other sites More sharing options...
cardona6569 Posted October 28, 2006 Share Posted October 28, 2006 Did you clean the MAF sensor? If you have not do that! www.lexls.com on complete instructions. C> PR The MAF resistance was within tolerance of the manual when I took it out to test it. I tested the resistance of both coils and they were within tolerance also. Would it be possible for a part's resistance to be within tolerance but the part is bad? Quote Link to comment Share on other sites More sharing options...
93ls400walt Posted October 28, 2006 Share Posted October 28, 2006 I have a 93ls and have had simular acceleration problems for the past 6 onths. I replaced the TPS, coils.wires, caps, rotors. plugs the intank gas screen the underbody fuel filter. Cleaned the throttle 3 times. Adjusted the tps multiple times. Changed vacum lines that I could see. Ran seafoam 5-6 times on a full tank of gas. Ran BG44k fuel cleaner Once on a full tank. All of these seamed to slightly improve my hesitation on acceleration problem. The most dramatic improvement, and I do mean dramatic, was when I ran Seafoam with just above 1/4 tank of gas. I accelerate now without the feeling that I am towing something. And the hesitation is very slight. And only now with hard acceleration. I would look into your fuel system. Quote Link to comment Share on other sites More sharing options...
zlilz Posted October 29, 2006 Author Share Posted October 29, 2006 cardona6569: Maybe i'm missing something, but I don't see a tutorial on www.lexls.com on how to clean the air flow meter. Isn't it an optical system? Do i just wipe it with rubbing alcohol? 93ls400walt: I have 1/4 tank of gas right now. I'll try running seafoam through it a couple times. It does seem like it's a problem with the fuel system. Would a motorvac cleaning help after I ran seafoam through it a couple times? I never had one done before, I have just heard about it. Quote Link to comment Share on other sites More sharing options...
93ls400walt Posted October 29, 2006 Share Posted October 29, 2006 The lexls tutorial is for a newer modle year. The MAF on our year ls's are different. Some have posted that spraying electrial contact cleaner through the small holes will clean the mirror and sensor that are located at the top of these holes. I had not had the courage to try that yet. I don't know anything about the motor vac. But you may find the site www.bgprod.com usefull. They have shops that will pressure clean your fuel system with their products. And also clean the EGR system. Which I think is the motor vac concept. Quote Link to comment Share on other sites More sharing options...
cardona6569 Posted October 29, 2006 Share Posted October 29, 2006 Hello: Here is the link to the tutorial is on the UK LEX forum, sorry about the other site: http://us.lexusownersclub.com/forums/index...view=getnewpost If yours is not exactly like the one ilustrated, use the same principles and clean everything contact and sensor itself with electronic contact cleaner. The electronic one will work just fine, can get it at autozone. Make sure everything is grease and dirt free; let the sensor dry and put it back on. C. PR The LEXLS.com site is great source for many things on your car model and year. I'm almost at the step where I want to take my 91 LS to the dealer and have them diagnose and fix it. Any ideas on where to start looking for problems would help. 2 months ago, I changed the timing belt myself. After the timing belt change, CEL error codes 13, 25 and 26 would show up occasionally. It didn't affect driving at all so I just ignored it. I noticed that sometimes driving on the highway, my foot would be in the same position, but for a second it felt like i lifted my foot off the gas pedal and placed it back on. Fast forward to now. The car still has the cel error codes. There seems to be two problems. Are they related? Problem 1: It starts fine and most of the time it's perfect. When the temperature is normal, sometimes all of the sudden the engine would act up. When the car is idling, all of the sudden as if the engine was no longer getting any air and was suffocating, the rpms will drop to 200 and stay that way for a second. Then the car will act as if the gas pedal was being pressed. It will rev up to about 1300 and then drop down to 600. Problem 2: While driving, all of the suddenly I loose power. Keeping my foot on the gas, there are periods when the engine seems to pick up and move and periods where nothing happens at all. Stepping and letting go of the gas pedal rapidly is very jerky but it seems to make the car move. I've looked around the engine and noticed the following: Spark plug wires are all under 25k resistance. The spark plugs on the passenger side bank all had a slightly damp black (carbon?) stuff on it. They do look a little old. The radiator cap has cracks in the rubber The transmission fluid is about .75 inches higher than the hot limit when the transmission is hot. I changed the rotor and the distributor a while back so they are fine. Resistance of the MAF is normal (according to the repair manual) The throttle position sensor's closed and .4mm open are normal. When it's fully open, it's an infinite resistance Engine coolant sensor is fine Using a timing gun and attaching it to spark plug wire 6, I see a 5 btdc which I know it's suppose to be higher than that ICV has a resistance of 50 So any ideas on what to look at next or replace? ECU? Fuel pump? TPS? ICV? changing the timing? Quote Link to comment Share on other sites More sharing options...
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